There has been proposed the method for forming color images on a thermal transfer image-receiving sheet which is dyeable with a sublimable dye by using a thermal transfer sheet composed of the sublimable dye as a recording agent and a substrate on which the sublimable dye is supported. In this method, the dye is heated using a thermal head of a printer as a heating means and transferred on the image-receiving sheet to obtain the color images. The thus formed images are very clear and excellent in transparency because of the dye used, and are therefore expected to provide high-quality images which are excellent in reproducibility of half tones and gradation.
In the dye receiving layer of some of the thermal transfer image-receiving sheets, polyesters are used from the viewpoint of an excellent dyeability thereof. As the thermal transfer image-receiving sheets using such polyesters, there are disclosed, for example, thermal transfer image-receiving sheets in which a dye receiving layer formed on a substrate sheet is produced from a dispersion prepared by dispersing a dye-acceptable resin such as polyesters obtained using ethylene glycol, etc., as raw components, in an aqueous medium (JP 6-135170A), thermal transfer dye-receiving sheets in which a dye receiving layer contains a polyester produced from a diol component containing an alkylene glycol adduct of bisphenol A and a dicarboxylic acid component containing terephthalic acid, and a crosslinked product thereof obtained by using an isocyanate compound as a crosslinking agent (JP 2933338), thermal transfer image-receiving sheets in which a dye receiving layer contains a polyester resin produced from a dicarboxylic acid component containing 40 mol % or more of an alicyclic dicarboxylic acid compound and a diol component containing 15 mol % or more of a diol compound having a bisphenol A backbone as a dye acceptable resin, and further contains a hydrogenated xylylene diisocyanate-modified product as a crosslinking agent (JP 2002-19306A), polyester films for sublimation-type heat-sensible recoding materials having a coating layer in which an aqueous oxazoline group-containing polymer is contained at a weight ratio of from 0.10 to 0.50 (JP 8-11447A), etc. In addition, it is also disclosed that a composition containing a polyester produced by using polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane as an alcohol component is used as a surface-treating agent for papers which is applied onto a printing medium for electrophotographic toners (Example 1 of JP 5-295100A).